Conventionally, as a method for accurately grinding semiconductor wafers, laser and optical prisms, various types of glass plates and metal plates, polishing by means of free abrasive grains has been applied.
As a typical example of the grinding apparatus, single side polishing will be described. A grinding surface plate which has an abrasive cloth affixed to its surface is driven and rotated on a horizontal surface, and an article being ground, which is connected to another flat plate to be driven and rotated, is slidably contacted to its surface. At the time of slidable contact, an abrasive liquid (a slurry of abrasive particles and a polishing solution) is supplied between the abrasive cloth and the article being ground to perform grinding.
As shown in FIG. 7 and FIG. 8, a conventional grinding surface plate 1 is fixed with at least 50 bolts 5, as it is adopted not to be disassembled on a semipermanent basis, onto a water cooled jacket 4 which is fixed with bolts 3 to a drive shaft 2 connected to an unillustrated drive. After assembling as described above, the grinding surface plate 1 is finish worked to a required dimensional accuracy. The abrasive cloth is affixed to the surface of the above-described grinding surface plate 1.
Meanwhile, in the case of polishing a semiconductor wafer for example, an accurate ground surface is formed by at lease either of the formation of a soft chemical product on the surface of the semiconductor wafer and the mechanical grinding with abrasive grains. Therefore, the surface of the grinding surface plate has its temperature increased to about 25 to 50 K. And, it is necessary to clean the remained abrasives from the surface of the abrasive cloth and to retain the abrasive cloth at appropriate hardness in order to achieve the uniform grinding of the semiconductor wafer surface. Accordingly, the abrasive cloth is frequently replaced as daily management.
The above-described conventional grinding surface plate cannot be easily removed from the grinding apparatus, and if the grinding surface plate is removed from the grinding apparatus, it is then necessary to adjust a dimensional accuracy, so that the above-described abrasive cloth replacing operation is necessarily performed on the grinding apparatus placed in a clean room. Therefore, it is difficult to secure an affixing accuracy of the abrasive cloth, and labor and time are highly required. In addition, the replacing operation in the cleaning room involves a disadvantage of degrading a clean level in the clean room. Particularly, the semiconductor wafer is becoming larger from year to year, being in a situation of entering an era of changing from 4 to 5-inch wafers to 8-inch wafers. Therefore, the grinding surface plate necessarily tends to be made large, making it more difficult to replace the abrasive cloth.
In view of above, as described in, for example, Japanese Patent Publication No. Hei 2-30827 and Japanese Patent Laid-Open Publication No. Hei 4-206929, it is proposed to separably configure the grinding disk with the abrasive cloth affixed and the surface plate body which is connected to a drive, and the grinding disk is removed from the surface plate body in order to make the abrasive cloth replacing operation. The separation type grinding surface plate which is described in Japanese Patent Publication No. Hei 2-30827 and Japanese Patent Laid-Open Publication No. Hei 4-206929 has pins fixed to the surface plate body inserted into holes formed on the circumference of the grinding disk to mechanically fix the circumference of the grinding disk, thereby attaching the grinding disk to the surface plate body. Therefore, when the grinding disk is thermally expanded due to heat generated at the grinding operation, there was a disadvantage that the center and its periphery of the grinding disk are deformed to bulge due to a temperature gradient between the grinding disk and the surface plate body, a differential thermal expansion between the grinding disk and the surface plate body, and the mechanical fixing of the circumference of the grinding disk. This deformation of the grinding disk naturally causes degradation of the grinding accuracy.
As described above, the conventional separation type grinding surface plate can facilitate-the cleaning and abrasive cloth replacing operations, but has a disadvantage that the grinding accuracy is easily deteriorated due to the deformation of the grinding disk caused by heat at the grinding operation.
An object of the present invention is to provide a separation type grinding surface plate which has achieved to secure an accuracy and save labor in the surface plate cleaning operation and abrasive cloth replacing operation and prevented a grinding accuracy from being deteriorated by a thermal deformation, and to provide a grinding apparatus using the same.